it should plane out, the catalpa I used recently was out side and was weathered, it took a lot of passes to get the grey out. I have used old pieces of pallets to make picture frames, ya know what those look like after they sat outside for a few years. run them threw a planer, looks like new. if you never used a planer make sure you take small passes and support the boards on both sides to eliminate snipe. I also like run 1 side through a joiner first. I like to keep the wood running smooth threw the planer and not have it drifting side to side. good luck dt.